Abstract: A rail lock riser assembly comprising a rail interface having a cutout, top surface with a through-hole, and shoulders; a first collar portion having a top outer tongue and a groove, a bottom outer tongue and a groove, mounting shoulders and a through-hole in the top outer tongue; a second collar having a top inner tongue and a groove, a bottom inner tongue and a groove, mounting shoulders and a through-hole in the top inner tongue; and a locking bolt. The collar portions are joined at the top outer tongue and groove and the bottom outer tongue and groove. The combined tongues of the first and second collar portions is inserted into the cutout of the rail interface and secured by the locking bolt.